Acyl coenzyme A carboxylase of Propionibacterium shermanii: detection and properties.

An acyl coenzyme A (CoA) carboxylase, which catalyzes the adenosine triphosphate-dependent fixation of CO2 into acetyl-, propionyl-, and butyryl-CoA, was detected in fractionated cell extracts of Propionibacterium shermanii. Catalytic activity was inhibited by avidin but was unaffected by avidin pretreated with excess biotin. The carboxylase levels detected were relatively small and were related to cellular growth. Maximal carboxylase activity was detected in cells grown for about 96 h. Thereafter, the activity declined rapidly. Optimal CO2 fixation occurred at pH 7.5. Other parameters of the assay system were optimized, and the apparent Km values for substrates were determined. The end product of the reaction (with acetyl-CoA as the substrate) was identified as malonyl-CoA. The stoichiometry of the reaction was such that, for every mole of acetyl-CoA and adenosine triphosphate consumed, 1 mol each of malonyl-CoA, adenosine diphosphate, and orthophosphate was formed. These data provide the first evidence for the presence of another biotin-containing enzyme, an acyl-CoA carboxylase, in these bacteria in addition to the well-characterized methylmalonyl-CoA carboxyltransferase.     

Characterization of a stable intermediate in the unfolding of diazoacetylglycine ethyl ester--pepsin by urea.

The irreversible unfolding of covalently inhibited swine pepsin by urea was studied by spectrophotometric and viscosity measurements. At pH 4.5 and 25 degrees C in 8 M urea, a stable intermediate form of the protein was detected. It differed from the native protein by a slight loss of secondary structure and an increased intrinsic viscosity ([pi] = 7.5 mL g-1), indicating the intermediate to have an increased molecular volume or to be more asymmetric in shape. The protein was transformed into a random coil form by increases of temperature and pH. Comparison with other results suggested that at pH 6 pepsin is less stable than its inactive precursor, pepsinogen, by about 3 Kcal mol-1 (1 cal = 4.187 J).     

Analysis of tadpole growth following gamma-ray irradiation

This investigation reports observations on the growth of Rana cyanophlyctis tadpoles following a whole body gamma-ray exposure. The effect on the body and hind limb size is perhaps the most significant of the period of latency. A dose of 2,000 R serves as a stressor and activates ACTH secretion in the tadpoles. The resultant somatotrophic hormone (STH) inhibition and subsequent recovery during the following days seem an integral part of the radiation syndrome.     

Thermodynamics of the denaturation of pepsinogen by urea.

The denaturation of swine pepsinogen has been studied as a function of urea concentration, pH, and temperature. The unfolding of the protein by urea has been found to be fully reversible under different conditions of pH, temperature, and denaturant concentration. Kinetic experiments have shown that the transition shows two-state behavior at 25 degrees C in the pH range 6-8 covered in this study. Analysis of the equilibrium data obtained at 25 degrees C according to Tanford (Tanford, C. (1970), Adv. Protein Chem. 24, 1) and Pace (Pace, N.C. (1975), Crit. Rev. Biochem. 3, 1) leads to the conclusion that the free energy of stabilization of native pepsinogen, relative to the denatured state, under physiological conditions, is only 6-12 kcal mol-1. The temperature dependence of the equilibrium constant for the unfolding of pepsinogen by urea in the range 20-50 degrees C at pH 8.0 can be described by assigning the following values of thermodynamic parameters for the denaturation at 25 degrees C: deltaH=31.5 kcal mol-1; deltaS=105 cal deg-1 mol-1; and deltaCp=5215 cal deg-1 mol-1.     

Utilization of F1 monosomics for genetic analyses involving awn expression,glume color,seed setting,and seed abortion in crosses of tetraploid and hexaploid wheats

Summary F₁ plants, monosomic for chromosomes 1A to 7B, from crosses of three lines of Triticum durum var. Khapli with the Chinese series were investigated together with their backcrosses to normal Chinese Spring. The three Khapli lines were designated K1-A, K1-B, and K1-D. Five parameters were analyzed: awn development, glume color, degree of selfing, crossing ability, and seed abortion.Morphological examination of F₁ monopentaploid plants revealed that, in the three lines, chromosomes 5A, 1B, 3B, 4B, 5B, and 6B had promotor genes and 2A, 6A, and 2B had inhibitor genes for awn development. Results on glume color suggested the presence of at least three inhibitor genes on 1B, 5B, and 7B, and three promotor genes on 3A, 6A, and 6B chromosomes of Chinese Spring.The first backcross of interspecific hybrids seemed to indicate that some chromosomes (1A, 1B, and 4B) originating from the Khapli lines possessed promotor genes, others (2B and 4A) carried inhibitor genes for seed setting. Similarily, the genetic factor (s) carried by chromosome 5A increased seed abortion whereas those on 2B and 6B reduced it.Self fertility in K1-D hybrids was probably the result of the inhibitor factor (s) on 7A and promotor genes on 3B, 4B, 5B, and 6B chromosomes coming from K1-D.     

Removal of heavy metals from industrial wastewater using microbial fuel cell

Removal efficiency of gold from a solution of pure tetrachloroaurate ions was investigated using microbial fuel cell (MFC) technology. The effects of type of catholyte solution and initial gold concentration on the removal efficiency were considered. Due to its presence at high levels in the gold wastewater, the effect of copper ions on the removal efficiency of the gold ions was also studied. The effects of pH and initial biomass concentration on the gold removal efficiency was also determined. The results showed that after 5 h contact time, 95% of gold removal efficiency from a wastewater containing 250 ppm of initial gold ions at ambient temperature using 80 g/L yeast concentration was achieved. After 48 h of the cell''s operation under the same condition, 98.86% of AuCl₄ ^– ions were successfully removed from the solution. At initial gold concentration in the waste solution of 250 ppm, pH 2, and initial yeast concentration of 80 g/L, 100% removal efficiency of the gold was achieved. On the other hand, the most suitable condition for copper removal was found at a pH of 5.2, where 53% removal efficiency from the waste solution was accomplished.